Signatures of emergent interfacial superconductivity in 45-degree twisted van der Waals Cuprate Superconductors

ORAL

Abstract

We developed a cryogenic assembly technique to fabricate Josephson Junctions with an atomically sharp twisted interface between Bi2Sr2CaCu2O8+x crystals. Transport measurements probing the interface revealed a suppressed but finite critical current close to 45 degrees. Fraunhofer patterns revealed anomalous junction effective thickness, which can be explained by a theoretical analysis that incorporates the second harmonic in the Josephson Energy versus phase relation. We study the change of Fraunhofer patterns as we vary applied in-plane magnetic field direction, probing the current distribution in the Josephson junction. Our theoretical analysis supports the dominant second harmonic in our Josephson Junctions, indicating time-reversal broken interfacial superconductivity.

*The experiments were supported by the NSF (DMR-1809188 and DMR-1922172)

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Publication: https://arxiv.org/abs/2108.13455
Twisted interfaces between stacked van der Waals cuprate crystals enable tunable Josephson coupling between in-plane anisotropic superconducting order parameters. Employing a novel cryogenic assembly technique, we fabricate Josephson junctions with an atomically sharp twisted interface between Bi2Sr2CaCu2O8+x crystals. The Josephson critical current density sensitively depends on the twist angle, reaching the maximum value comparable to that of the intrinsic junctions at small twisting angles, and is suppressed by almost 2 orders of magnitude yet remains finite close to 45 degree twist angle. Through the observation of fractional Shapiro steps and the analysis of Fraunhofer patterns we show that the remaining superconducting coherence near 45 degree is due to the co-tunneling of Cooper pairs, a necessary ingredient for high-temperature topological superconductivity.

Presenters

  • Alex cui

    • Harvard University

Authors

  • Alex cui

    • Harvard University

  • Shu Yang Frank Zhao

    • Harvard University

  • Pavel A Volkov

    • Rutgers University

  • Jed Pixley

    • Rutgers University

  • Nicola Poccia

    • IFW Dresden

  • Philip Kim

    • Harvard University

  • Genda Gu

    • Brookhaven National Laboratory
    • Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY 11973, USA

  • Ruidan Zhong

    • Shanghai Jiaotong University

  • Sangmin Lee

    • Seoul National University

  • Hyobin Yoo

    • Sogang University

  • Jules A Gardener

    • Harvard CNS

  • Austin Akey

    • Harvard CNS

  • Rebecca Engelke

    • Harvard University

  • Yuval Ronen

    • Harvard University

  • Marcel Franz

    • University of British Columbia

  • Tarun Tummuru

    • University of British Columbia

  • Stephan Plugge

    • University of British Columbia